It is the goal of this project to develop methods that allow the directed growth in vitro of ordered and optically defined two-dimensional nerve cell networks in which all neurons can be stimulated and from which all major extracellular electrical activity can be simultaneously and continuously monitored for days and possibly weeks. The achievement of these goals would make possible a systematic investigation of network information storage and processing as well as the pharmacological manipulation of these phenomena. It is proposed that the conventional electrophysiological recording techniques be deemphasized in favor of fixed-matrix, recessed-tip, multimicroelectrode surfaces that have already been successfully tested. It is also proposed that ordered networks be obtained by utilizing laser microbeam methods for cell elimination, neurite transection and production of adhesion islands and pathways on surfaces. Enough preliminary data has been gathered to prove that these methods are applicable. The utilization of the laser microbeam system gives the experimenter a heretofore unattainable manipulative finesse that can be conveniently applied to influence growing neuronal systems in closed chambers.